// Copyright (c) 2011 The LevelDB Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file. See the AUTHORS file for names of contributors.\

#include "util/logging.h"

#include <cstdarg>
#include <cstdio>
#include <cstdlib>
#include <limits>

#include "leveldb/env.h"
#include "leveldb/slice.h"

namespace leveldb {

void AppendNumberTo(std::string* str, uint64_t num) {
    char buf[30];
    std::snprintf(buf, sizeof(buf), "%llu", static_cast<unsigned long long>(num));
    str->append(buf);
}

void AppendEscapedStringTo(std::string* str, const Slice& value) {
    for (size_t i = 0; i < value.size(); ++i) {
        char c = value[i];
        if (c >= ' ' && c <= '~') {
            str->push_back(c);
        } else {
            char buf[10];
            std::snprintf(buf, sizeof(buf), "\\x%02x",
                          static_cast<unsigned int>(c) & 0xff);
            str->append(buf);
        }
    }
}

std::string NumberToString(uint64_t num) {
    std::string r;
    AppendNumberTo(&r, num);
    return r;
}

std::string EscapeString(const Slice& value) {
    std::string r;
    AppendEscapedStringTo(&r, value);
    return r;
}

bool ConsumeDecimalNumber(Slice* in, uint64_t* val) {
    // Constants that will be optimized away.
    constexpr const uint64_t kMaxUint64 = std::numeric_limits<uint64_t>::max();
    constexpr const char kLastDigitOfMaxUint64 = 
        '0' + static_cast<char>(kMaxUint64 % 10);
    
    uint64_t value = 0;

    // reinterpret_cast-ing from char* to uint8_t* to avoid signedness.
    const uint8_t* start = reinterpret_cast<const uint8_t*>(in->data());

    const uint8_t* end = start + in->size();
    const uint8_t* current = start;
    for (; current != end; ++current) {
        const uint8_t ch = *current;
        if (ch < '0' || ch > '9') break;

        // Overflow check.
        // kMaxUint64 / 10 is also constant and will be optimized away.
        if (value > kMaxUint64 / 10 ||
            (value == kMaxUint64 / 10 && ch > kLastDigitOfMaxUint64)) {
                return false;
        }

        value = (value * 10) + (ch - '0');
    }

    *val = value;
    const size_t digits_consumed = current - start;
    in->remove_prefix(digits_consumed);
    return digits_consumed != 0;
}

}  // namespace leveldb
